This invention relates to the field of high performance switching systems, and more particularly to a "smart" multiple matrix switching system which permits implementation of universal pin concepts in conjunction with the utilization of automatic test equipment (ATE).
Typically, sophisticated ATE configured as an automatic test station finds wide application in the avionics instrumentation field. Examples of such ATE are found in the computerized automatic testers (CAT-series) sold by the assignee herein, Grumman Aerospace Corporation. Automatic testing of the various electronic systems and subsystems of an aircraft may be readily conducted by means of such automatic test equipment.
The test interface is that portion of the ATE where the unit under test (UUT) is connected. It is apparent that the tradeoff between interface versatility and simplicity of ATE hardware presents a somewhat difficult design problem. On the one hand, it is desirable to have a versatile interface that minimizes or eliminates the use of interface adapters. On the other hand, such an interface can be so complex it could reduce the reliability, in increase the cost, and degrade the frequency performance of the ATE system.
An optimal switching system for connecting a UUT would have several basic capabilities. First, the test interface should be reliable and maintainable. High-current hot switching should be segregated from signal switching to increase switching component life. Moreover, the hardware portion of the test interface should be simple with as few parts as possible; it must also have superior test and fault isolation characteristics.
Second, the test interface should possess certain performance characteristics, such as, for example, signal path repeatability. No matter how many times a program is recompiled, the signal paths should remain constant. It should provide signal fidelity and be capable of performing the interface function at fundamental switching frequencies up to 20 MHz along with low cross talk and insertion loss. It also should have functional flexibility for signal routing and switching.
Third, the test interface should be compatible with the software. It should work in a high level language environment, such as, for example, ATLAS, operate off the IEEE-488 interface bus and be easy to program. And finally, the test interface should be low in cost.
The current state-of-the-art for automatic test systems has addressed and solved many traditional ATE problems. The "electronics behind the pin" concept has given rise to the "universal pin" with all its inherent advantages including simplification of the system/UUT interface, flexibility, and minimization of programmer and operator involvement with the connection process. Simultaneously with the advent of the universal pin, improvements have been made in the ATE instrumentation field. These improvements have not been limited to instrument performance, but include the ability to easily integrate and merge these increased capabilities into an effective test system through the use of the IEEE-488 bus. Unfortunately, universal pin test systems can make little use of these enhanced instrument capabilities because the instrumentation is often provided by unique and custom designed electronics behind each universal pin.
It is believed that prior to the present invention, there has not been available a switching system that would take advantage of such state-of-the-art instrument capabilities in a universal pin system.
It is accordingly a general object of the present invention to provide a switching system which has characteristics more nearly approaching the optimal attributes described above, particularly those applicable to ATE applications.
It is a particular object of the invention to provide a multiple matrix switching system having a universal pin interface, i.e., all instrument capabilities available at each interface pin, between the UUT and a multiplicity of instruments.
Other objects will be apparent in the following detailed description and the practice of the invention.